Mars Global Surveyor
Mars Orbiter Camera

Comparision of Mariner 9 and MOC Views of Ganges Crater Central Mound

MGS MOC Release No. MOC2-265M, 4 December 2000


Ganges Chasma is part of the Valles Marineris trough system that stretches nearly 5,000 kilometers (3,000 miles) across the western equatorial region of Mars. Near the center of Ganges Chasma is a mound of light-toned, layered rock. It has been known since the Mariner 9 mission that this light material is piled nearly as high as the outside rims of the chasm. A "3-D" view of the mound can be seen in Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) release, "Ganges Chasma in 3-D," MOC2-139, 25 June 1999.

While it was known from Mariner 9 images---such as the subframe of the Mariner 9 picture above (Orbit 207, B-camera, image 15)---that the mound appears to be layered, MGS MOC images show that the features once thought to indicate layering are illusions. A portion of MOC image M04-00323 is shown at the center, with an expanded view at the right. The white box in the Mariner 9 view is 3 km (1.9 mi) wide and shows the location of the center MOC image; the white box in the center image is 1.3 km (0.8 mi) wide and shows the location of the view on the right. The light-toned material is in fact layered, but at a scale invisible to the Mariner 9 and Viking cameras. The features seen in Mariner 9 images and interpreted to be dark layers turn out, as seen in the MOC images, to be thin veneers of sand and dark mantling material resting on top of light-toned, thinly-layered and massive rock units. The pictures are illuminated from the upper left.

Image Credit: NASA/JPL/Malin Space Science Systems

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

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